Automatic transmission fluid

ABSTRACT

An automatic transmission fluid contains: a base oil: a component (A) that is two or more succinimides each having an alkenyl group or an alkyl group, wherein a mass average molecular weight of the alkenyl group or the alkyl group is different in each of the succinimides; a component (B) that is a primary amine having a carbon chain having 12 to 24 carbon atoms; a component (C) that is an aliphatic amine alkylene oxide adduct having a carbon chain having 12 to 20 carbon atoms; and a component (D) that is an amide compound.

TECHNICAL FIELD

The present invention relates to an automatic transmission fluid.

BACKGROUND ART

In recent years, many automatic transmissions including a lock-up clutch have come to be used in order to improve fuel efficiency. However, in the lock-up clutch, deterioration of an automatic transmission fluid is liable to deteriorate μ-V characteristics between a paper disc and a metal plate to generate self-excited oscillation (shudder). Accordingly, the automatic transmission fluid contains a friction modifier for decreasing a friction coefficient in a low speed zone in order to keep so-called μ-V characteristics in a positive gradient.

There has been proposed an automatic transmission fluid composition in which N-substituted dialkanolamine is added to a base oil having an adjusted viscosity in order to reduce a friction coefficient in a low speed zone, thereby maintaining a favorable shift feeling for a long time (see Patent Literature 1).

The lock-up clutch and a transmission clutch are required to have a high clutch capacity in order to provide an automatic transmission in a compact size. For instance, there has been proposed a power transmission fluid containing a primary amine as an initial friction modifier and dialkanolamine as a friction modifier exhibiting effects after elapse of time (see Patent Literature 2).

However, when a content of the friction modifier is decreased in order to increase the clutch capacity, a shudder prevention lifetime is shortened. In other words, in the automatic transmission fluid, prolonging the shudder prevention lifetime of the lock-up clutch is in a trade-off relationship with increasing the clutch capacity of the lock-up clutch.

Accordingly, there has been proposed an automatic transmission fluid composition containing a predetermined carboxylic acid glyceride, thereby simultaneously providing both a high clutch capacity and a long shudder prevention lifetime in the lock-up clutch (see Patent Literature 3).

CITATION LIST Patent Literature(S)

-   Patent Literature 1: JPl-259096A -   Patent Literature 2: JP2001-515099A -   Patent Literature 3: JP2003-82375A

SUMMARY OF THE INVENTION Problem(s) to be Solved by the Invention

However, even with the automatic transmission fluid composition disclosed in Patent Literature 3, a high clutch capacity and a long shudder prevention lifetime of the lock-up clutch were unable to be sufficiently exhibited at the same time.

An object of the invention is to provide an automatic transmission fluid capable of sufficiently exhibiting a high clutch capacity and a long shudder prevention lifetime in the lock-up clutch at the same time.

Means for Solving the Problem(s)

In order to solve the above problem, an object of the invention is to provide an automatic transmission fluid containing: a base oil; a component (A) that is two or more succinimides each having an alkenyl group or an alkyl group, in which a mass average molecular weight of the alkenyl group or the alkyl group is different in each of the succinimides; a component (B) that is a primary amine having a carbon chain having 12 to 24 carbon atoms; a component (C) that is an aliphatic amine alkylene oxide adduct having a carbon chain having 12 to 20 carbon atoms; and a component (D) that is an amide compound.

The automatic transmission fluid of the invention can sufficiently exhibit a high clutch capacity and a long shudder prevention lifetime in the lock-up clutch at the same time.

DESCRIPTION OF EMBODIMENT(S)

An automatic transmission fluid according to an exemplary embodiment of the invention (hereinafter, also referred to as “the present transmission fluid”) will be described in detail below.

It should be noted that the automatic transmission fluid according to the exemplary embodiment obtained by blending components means not only an automatic transmission fluid containing the components, but also an automatic transmission fluid containing a modified substance obtained by modifying at least one of the components in place of the at least one of the components, and an automatic transmission fluid containing a reactant obtained by reaction of at least two of the components.

Base Oil

A base oil used for the present transmission fluid is not particularly limited but may be a mineral oil or a synthetic oil. The mineral oil is preferably so-called highly-refined mineral oil, examples of which are: refined oil provided by refining oil fractions in accordance with an ordinary method; deeply-dewaxed oil provided by deeply dewaxing the refined oil fractions; and hydrotreated oil provided by hydrotreating the oil fractions, the oil fractions being provided by atmospherically distilling paraffin-base crude oil, intermediate-base crude oil or naphthene-base crude oil or by vacuum-distilling the residual oil of the atmospherically-distilled oil. A refining method for the above mineral oil is not particularly limited but various methods may be employed. One of the mineral oils may be used alone or two or more thereof may be used in a mixture.

Examples of the synthetic oil include alkylbenzene, alkyl naphthalene, poly-α-olefin, polyvinyl ether, polyalkylene glycol, polycarbonate, and polyol ester. One of the synthetic oils may be used alone, or two or more thereof may be used in a mixture.

The mineral oil and the synthetic oil may be mixed. A kinematic viscosity at 100 degrees C. of the base oil is preferably in a range from 1.5 mm²/s to 4 mm²/s, more preferably from 2.1 mm²/s to 3.5 mm²/s, further preferably from 2.5 mm²/s to 3 mm²/s. When the kinematic viscosity at 100 degrees C. of the base oil is 1.5 mm²/s or more, wear of sliding portions such as a gear bearing and a clutch of a transmission can be lessened. Moreover, when the kinematic viscosity at 100 degrees C. of the base oil is 4 mm²/s or less, a low-temperature viscosity can be sufficiently decreased. It should be noted that the kinematic viscosity at 100 degrees C. of the base oil is measured in accordance with JIS K2283 (2000).

Component (A)

A component (A) used in the present transmission fluid is two or more succinimides each having an alkenyl group or an alkyl group, in which a mass average molecular weight of the alkenyl group or the alkyl group is different in each of the succinimides. The component (A) functions as a dispersant. However, use of a single succinimide is not sufficient to solve the problem of the invention. Mono-succinimide is preferable as the succinimide. For instance, alkenyl succinimide or alkyl succinimide, which is represented by a formula (1) below, is more preferable.

In the formula (1), R¹ represents an alkenyl group or an alkyl group having a mass average molecular weight in a range from 800 to 1500.

When the mass average molecular weight of R¹ is 800 or more, a clutch capacity can be kept high and solubility of the component (A) in the base oil is improved. When the mass average molecular weight of R¹ is 1500 or less, a shudder prevention lifetime can be prolonged and dispersibility is improved.

As the component (A), it is preferable to use a mono-succinimide (A1) having an alkenyl group or an alkyl group having a mass average molecular weight in a range from 1200 to 1500 in combination with a mono-succinimide (A2) having an alkenyl group or an alkyl group having a mass average molecular weight in a range from 800 to less than 1200. The mass average molecular weight of the alkenyl group or the alkyl group in the component (A1) is preferably in a range from 1250 to 1450, further preferably from 1300 to 1400. The mass average molecular weight of the alkenyl group or the alkyl group in the component (A2) is preferably in a range from 850 to 1150, further preferably from 900 to 1100.

When the components (A1) and (A2) are used in combination and further later-described components (B), (C) and (D) are contained, both a high clutch capacity and a long shudder prevention lifetime of the lock-up clutch can be sufficiently obtained.

Herein, R² is preferably an alkylene group having 2 to 5 carbon atoms. m is preferably an integer from 1 to 10, more preferably 2 to 5, further preferably 3 or 4. When m is 1 or more, dispersibility is favorable. When m is 10 or less, solubility of the component (A) in the base oil is favorable.

Examples of the alkenyl group include a polybutenyl group, a polyisobutenyl group, and an ethylene-propylene copolymer. Examples of the alkyl group include an alkyl group obtained by hydrogenating a polybutenyl group, a polyisobutenyl group, and an ethylene-propylene copolymer. The alkenyl group is preferably a polybutenyl group or a polyisobutenyl group. The polyisobutenyl group is preferably obtained in a form of a mixture of 1-butene and isobutene or a polymer of highly pure isobutene. A preferable example of the alkyl group is represented by an alkyl group obtained by hydrogenating a polybutenyl group or polyisobutenyl group. A mass average molecular weight of each of the alkenyl group and the alkyl group is easily obtained according to GPC.

The above alkenyl succinimide or alkyl succinimide can be typically manufactured by reacting polyamine with alkenyl succinic anhydride, which is obtained by reacting polyolefin with maleic anhydride, or alkyl succinic anhydride, which is obtained by hydrogenating the alkenyl succinic anhydride.

As an olefin monomer forming the above polyolefin, a single α-olefin having 2 to 8 carbon atoms may be used or two or more thereof may be used in a mixture. Preferably, a mixture of isobutene and butene-1 is usable.

Examples of the polyamine include: monodiamine such as ethylene diamine, propylene diamine, butylene diamine, and pentylene diamine; and polyalkylene polyamine such as diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, di(methylethylene)triamine, dibutylenetriamine, tributylene tetramine, and pentapentylene hexamine.

Component (B)

The component (B) of the present transmission fluid is a primary amine having a carbon chain having 12 to 24 carbon atoms. The component (B) functions as a friction modifier in the present transmission fluid. When the carbon atoms of the carbon chain are 12 or more, μ-V characteristics of the lock-up clutch are favorable and the component (B) is easily soluble in the base oil. Accordingly, the carbon atoms of the carbon chain are preferably 14 or more, more preferably 16 or more. On the other hand, when the carbon atoms of the carbon chain are 24 or less, both a clutch capacity of a transmission clutch and the pt-V characteristics of the lock-up clutch are likely to be satisfactory. Accordingly, the carbon atoms of the carbon chain are preferably 22 or less, more preferably 20 or less.

The primary amine of the component (B) is preferably aliphatic primary amine, which may be aliphatic primary alkyl amine or aliphatic primary alkenyl amine. The alkyl group and the alkenyl group may be linear or branched. However, the alkyl group and the alkenyl group are preferably linear in order to improve the μ-V characteristics of the lock-up clutch.

Examples of the alkyl amine and the alkenyl amine include n-dodecyl amine, n-tridecyl amine, n-tetradecyl amine, 2-methyl-n-tridecyl amine, n-pentadecyl amine, n-hexadecyl amine, n-heptadecyl amine, n-octadecyl amine, isooctadecyl amine, n-nonadecyl amine, n-icosylamine, n-octadecenyl amine, stearyl amine and oleyl amine.

Moreover, the component (B) may react with acid phosphate or acid phosphite to form an amine salt. Examples of the acid phosphate include 2-ethylhexyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, isodecyl acid phosphate, lauryl acid phosphate, tridecyl acid phosphate, stearyl acid phosphate, and isostearyl acid phosphate. Examples of the acid phosphite include ethyl hydrogen phosphite, n-propyl hydrogen phosphite, n-butyl hydrogen phosphite, 2-ethylhexyl hydrogen phosphite, di-2-ethylhexyl hydrogen phosphite, dilauryl hydrogen phosphite, and dioleyl hydrogen phosphite.

Component (C)

The component (C) of the present transmission fluid is an aliphatic amine alkylene oxide adduct having a carbon chain having 12 to 20 carbon atoms. The component (C) functions as a friction modifier in the present transmission fluid.

The component (C) is obtainable by adding an alkylene oxide to aliphatic amine having a carbon chain having 12 to 20 carbon atoms by an ordinary method. The above aliphatic amine is preferably aliphatic primary amine, which may be linear or branched and saturated or unsaturated.

Specific examples of the primary amine include n-dodecyl amine, n-tridecyl amine, n-tetradecyl amine, 2-methyl-n-tridecyl amine, n-pentadecyl amine, n-hexadecyl amine, n-heptadecyl amine, n-octadecyl amine, isooctadecyl amine, n-nonadecyl amine, n-icosylamine, n-octadecenyl amine, stearyl amine and oleyl amine. One of the primary amines may be used alone, or two or more thereof may be used in a mixture. The mixture of two or more of the primary amine is exemplified by an aliphatic primary amine derived from animal oil and vegetable oil such as beef tallow amine, hardened beef tallow amine, coconut oil amine, palm oil amine and soybean oil amine. The primary amine is desirably refined by distillation.

The alkylene oxide of the present transmission fluid is preferably an alkylene oxide having 2 to 4 carbon atoms (EO: ethylene oxide, PO: propylene oxide and BO: butylene oxide) which is easily reactive in an addition reaction and easily obtainable. EO is particularly preferable in terms of the μ-V characteristics of the lock-up clutch. One of the alkylene oxides having 2 to 4 carbon atoms may be used alone, or two or more thereof may be used in a mixture. When two or more of the alkylene oxides are used, the alkylene oxides may be added in a form of a block or at random.

Component (D)

The component (D) used in the present transmission fluid is an amide compound. The component (D) functions as a friction modifier in the present transmission fluid.

The amide compound as the component (D) is preferably an amide of aliphatic carboxylic acid, in which an aliphatic group is preferably an alkyl group or an alkenyl group. The alkyl group or an alkenyl group preferably has 12 to 20 carbon atoms in terms of a friction coefficient. Examples of the component (D) include stearic acid amide, isostearic acid amide, lauric acid amide, myristic acid amide, palmitic acid amide and oleic acid amide. One of the amide compounds may be used alone, or two or more thereof may be used in combination.

Present Transmission Fluid

Since the present transmission fluid contains the base oil, the component (A), the component (B), the component (C), and the component (D), the shudder prevention lifetime of the lock-up clutch can be kept for a long time and further a high clutch capacity of the transmission clutch can be maintained.

A content of the component (A) is preferably in a range from 4.5 mass % to 6 mass % based on a total amount of the present transmission fluid, more preferably from 4.75 mass % to 5.75 mass %, further preferably from 5 mass % to 5.5 mass %. When the content of the component (A) falls within the above range, the shudder prevention lifetime of the lock-up clutch can be kept for a longer time and a higher clutch capacity of the transmission clutch can be maintained.

When the mono-succinimide (A1) having an alkenyl group or an alkyl group having a mass average molecular weight in a range from 1200 to 1500 and the mono-succinimide (A2) having an alkenyl group or an alkyl group having a mass average molecular weight in a range from 800 to less than 1200 are used as the component (A), a blending ratio of the component (A1) is preferably in a range from 50 mass % to 80 mass % based on a total amount of the components (A1) and (A2), more preferably in a range from 55 mass % to 75 mass %. When the blending ratio between the component (A1) and the compound (A2) falls within the above range, the shudder prevention lifetime of the lock-up clutch can be kept for a longer time and a higher clutch capacity of the transmission clutch can be maintained.

A content of the component (B) is preferably in a range from 24 mass ppm to 235 mass ppm in terms of a nitrogen amount based on the total amount of the present transmission fluid in order to improve the μ-V characteristics of the lock-up clutch, more preferably in a range from 26 mass ppm to 226 mass ppm, further preferably in a range from 28 mass ppm to 210 mass ppm.

A content of the component (C) is preferably in a range from 10 mass ppm to 320 mass ppm in terms of a nitrogen amount based on the total amount of the total amount of the present transmission fluid in order to improve the μ-V characteristics of the lock-up clutch, more preferably in a range from 12 mass ppm to 300 mass ppm, further preferably in a range from 14 mass ppm to 280 mass ppm.

A content of the component (D) is preferably in a range from 62 mass ppm to 310 mass ppm in terms of a nitrogen amount based on the total amount of the total amount of the present transmission fluid in order to improve the pt-V characteristics of the lock-up clutch, more preferably in a range from 70 mass ppm to 300 mass ppm, further preferably in a range from 80 mass ppm to 290 mass ppm.

A kinematic viscosity at 100 degrees C. of the present transmission fluid is preferably in a range from 3.5 mm²/s to 10 mm²/s, more preferably from 4 mm²/is to 8.5 mm²/s, further preferably from 4.5 mm²/s to 7.5 mm²/s. When the kinematic viscosity at 100 degrees C. of the present transmission fluid is 10 mm²/s or less, a low-temperature viscosity can be sufficiently decreased. When the kinematic viscosity at 100 degrees C. of the present transmission fluid is 3.5 mm²/s or more, wear of sliding portions such as a gear bearing and a clutch of a continuously variable transmission can be lessened. It should be noted that the kinematic viscosity at 100 degrees C. of the present transmission fluid is measured in accordance with JIS K2283 (2000).

Since the present transmission fluid has a high clutch capacity (torque transmission capacity) and a long shudder prevention lifetime, the present transmission fluid is suitably used in various continuously variable transmissions such as a belt-type continuously variable transmission (push-type and chain-type) using a metallic belt or a toroidal continuously variable transmission. The present transmission fluid is particularly suitable for a continuously variable transmission having a torque convertor provided with a lock-up clutch. Moreover, the present transmission fluid is also suitable for a stepped automatic transmission since having a high clutch capacity of a transmission clutch and a long shudder prevention lifetime of the lock-up clutch.

Component (E)

It is preferable that the present transmission fluid further contains a tertiary amine as a component (E). ©A friction coefficient in a low speed zone can be further decreased by containing the tertiary amine. The tertiary amine as the component (E) is preferably represented by a formula (2) below.

R³R⁴NR⁵  (2)

In the formula, R³ is a hydrocarbon group preferably having 12 or more carbon atoms, more preferably 14 or more carbon atoms, further preferably 16 or more carbon atoms. When the carbon atoms of R³ fall within the above range, the μ-V characteristics of the lock-up clutch are effectively improvable. In order to decrease the friction coefficient, the carbon atoms of R³ are preferably 28 or less, more preferably 24 or less, further preferably 20 or less.

Examples of the hydrocarbon group include an alkyl group, alkenyl group, aryl group, and aralkyl group. Among the hydrocarbon group, an aliphatic hydrocarbon group is preferable, among which an aliphatic hydrocarbon group having a saturated structure is particularly preferable. Accordingly, R³ is exemplified by a hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, heneicosyl group, and docosyl group, among which an octadecyl group is most preferable.

A carbon chain of R³ may be in a linear structure or a branched structure, among which a carbon chain in a linear structure is preferable.

Both R⁴ and R⁵ are hydrocarbon groups each having 4 or less carbon atoms. Preferably, R⁴ and R⁵ each independently have 1 or 2 carbon atoms. Specifically, R⁴ and R⁵ are exemplified by a methyl group, ethyl group and vinyl group. When the carbon atoms of each of R⁴ and R⁵ fall within the above range, the shudder prevention effect can be strongly exhibited. Moreover, in view of stability, a methyl group or an ethyl group is preferred to a vinyl group having an unsaturated structure. It should be noted that the respective terminals of R⁴ and R⁵ may be bonded to each other to form a ring.

Specific examples of the component (E) include dimethylhexadecylamine, dimethyloctadecylamine, dimethylheneicosylamine, diethyloctadecylamine, and methylethyloctadecylamine. One of the tertiary amines may be contained alone as the component (E) in the present transmission fluid, or two or more of the tertiary amine may be used in combination.

A nitrogen amount derived from the component (E) is preferably 10 mass ppm or more in terms of nitrogen based on the total amount of the present transmission fluid in consideration of the shudder prevention effect and the prolonging effect of the shudder prevention lifetime, more preferably 15 mass ppm or more, further preferably 20 mass ppm or more. However, excessive increase in the content of the component (E) saturates the prolonging effect of the shudder prevention lifetime. Accordingly, the nitrogen amount derived from the component (E) is desirably limited to 100 mass ppm or less.

The present transmission fluid can further contain various additives. Examples of the additives include a viscosity index improver, a pour point depressant, an antioxidant, an oiliness agent, an extreme pressure agent, a detergent dispersant, a rust inhibitor, a metal deactivator, and an antifoaming agent.

Examples of the viscosity index improver include polymethacrylate, dispersed polymethacrylate, olefin copolymer (e.g. ethylene-propylene copolymer), dispersed olefin copolymer and styrene copolymer (e.g. styrene-diene copolymer and styrene-isoprene copolymer). A content of the viscosity index improver is approximately in a range from 0.5 mass % to 15 mass % in terms of a resin amount based on the total amount of the present transmission fluid in view of the blending effect.

The pour point depressant is exemplified by polymethacrylate having a mass average molecular weight of 10000 to 150000. A content of the pour point depressant is approximately in a range from 0.01 mass % to 10 mass % of the total amount of the present transmission fluid in view of the blending effect.

Examples of the antioxidant include an aminic antioxidant, a phenolic antioxidant, a phosphorous antioxidant and a sulfuric antioxidant which are used in a typical hydrocarbon lubricating oil. One of the antioxidants may be used alone or two or more thereof may be used in combination. Examples of the aminic antioxidant include: monoalkyldiphenylamine compounds such as monooctyldiphenylamine and monononyldiphenylamine; dialkyldiphenylamine compounds such as 4,4-dibutyldiphenylamine, 4,4-dipentyldiphenylamine, 4,4-dihexyldiphenylamine, 4,4-diheptyldiphenylamine, 4,4-dioctyldiphenylamine and 4,4-dinonyldiphenylamine; polyalkyldiphenylamine compounds such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine and tetranonyldiphenylamine; and naphthylamine compounds such as alpha-naphthylamine, phenyl-alpha-naphthylamine, butylphenyl-alpha-naphthylamine, pentylphenyl-alpha-naphthylamine, hexylphenyl-alpha-naphthylamine, heptylphenyl-alpha-naphthylamine, octylphenyl-alpha-naphthylamine and nonylphenyl-alpha-naphthylamine.

Examples of the phenolic antioxidant include: monophenol compounds such as 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butyl-4-ethylphenol; and diphenol compounds such as 4,4-methylenebis(2,6-di-tert-butylphenol) and 2,2-methylenebis(4-ethyl-6-tert-butylphenol).

Examples of the sulfuric antioxidant include: 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazine-2-ylamino)phenol; a thioterpene compound such as a reaction product of phosphorus pentasulfide and pinene; and dialkylthiodipropionate such as dilaurylthiodipropionate and distearylthiodipropionate.

Examples of the phosphorous antioxidant include triphenyl phosphite, diethyl[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate.

A content of the antioxidant is preferably in a range from 0.01 mass % to 10 mass % based on the total amount of the present transmission fluid in view of the blending effect, more preferably from 0.03 mass % to 5 mass %.

Examples of the oiliness agent include: aliphatic alcohol; fatty acid compound such as fatty acid and fatty acid metal salt; an ester compound such as polyol ester, sorbitan ester, and glyceride; and an amine compound such as aliphatic amine A content of the oiliness agent is preferably in a range from 0.1 mass % to 30 mass % based on the total amount of the present transmission fluid in view of the blending effect, more preferably from 0.5 mass % to 10 mass %.

Examples of the extreme pressure agent include a sulfuric extreme pressure agent, a phosphorous extreme pressure agent, an extreme pressure agent containing sulfur and metal, and an extreme pressure agent containing phosphorus and metal. One of the extreme pressure agents may be used alone or two or more thereof may be used in combination. It is only necessary that the extreme pressure agent contains at least one of a sulfur atom and a phosphorus atom in a molecule and can exhibit load bearing performance and wear resistance. Examples of the extreme pressure agent in a molecule include sulfurized fat and oil, sulfurized fatty acid, ester sulfide, olefin sulfide, dihydrocarbyl polysulfide, thiadiazole compound, alkylthiocarbamoyl compound, triazine compound, thioterpene compound, and dialkylthiodipropionate compound.

Examples of the extreme pressure agent containing sulfur and metal and the extreme pressure agent containing phosphorus and metal include zinc dialkylthiocarbamate (Zn-DTC), molybdenum dialkylthiocarbamate (Mo-DTC), lead dialkylthiocarbamate, tin dialkylthiocarbamate, zinc dialkyldithiophosphate (Zn-DTP), molybdenum dialkyldithiophosphate (Mo-DTP), sodium sulfonate and calcium sulfonate. A representative example of the extreme pressure agent containing phosphorus in a molecule is phosphates (e.g., tricresyl phosphate) and amine salts thereof. A content of the extreme pressure agent is preferably in a range from 0.01 mass % to 30 mass % based on the total amount of the present transmission fluid in view of the blending effect and economy, more preferably from 0.01 mass % to 10 mass %.

Examples of the detergent dispersant include metal sulfonate, metal salicylate, metal phenate and succinimide. A content of the detergent dispersant is preferably in a range from 0.01 mass % to 30 mass % in terms of metal based on the total amount of the present transmission fluid in view of the blending effect, more preferably from 0.05 mass % to 10 mass %.

Examples of the rust inhibitor include a metal sulfonate, succinate, alkyl amine and alkanolamine such as monoisopropanolamine. A content of the rust inhibitor is preferably in a range from 0.01 mass % to 10 mass % based on the total amount of the present transmission fluid in view of the blending effect, more preferably from 0.05 mass % to 5 mass %.

Examples of the metal deactivator include benzotriazole and thiadiazole. A content of the metal deactivator is preferably in a range from 0.01 mass % to 10 mass % based on the total amount of the present transmission fluid in view of the blending effect, more preferably from 0.01 mass % to 1 mass %.

Examples of the antifoaming agent include methyl silicone oil, fluorosilicone oil and polyacrylate. A content of the antifoaming agent is preferably in a range from 0.0005 mass % to 0.01 mass % of the total amount of the present transmission fluid in view of the blending effect.

EXAMPLES

Next, the invention will be described in more detail with reference to Examples and Comparatives, but the scope of the invention is by no means limited to the description of Examples and Comparatives.

Examples 1 to 6 and Comparatives 1 to 4

Sample oils intended as a transmission fluid were prepared at blending ratios shown in Table 1. A kinematic viscosity at 100 degrees C. of each of the sample oils was in a range from 5.5 mm²/s to 5.6 mm²/s as shown in Table 1.

TABLE 1 Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 1 2 3 4 Blending Base oil ¹⁾ bal- bal- bal- bal- bal- bal- bal- bal- bal- bal- composition ance ance ance ance ance ance ance ance ance ance of sample Dispersant Dispersant A1²⁾  3.00  3.00  3.00  3.00  3.00  2.50 — 5.00 3.00 3.00 oils (mass %) Dispersant A2³⁾  2.00  2.00  2.00  2.00  2.00  2.50  5.00 — 2.00 2.00 Friction Friction 56   38   56   56   56   56   56   56 — 56 modifier modifier B⁴⁾ (in terms of N, Friction 20   20   20   14   20   20   20   20 20 20 mass ppm) modifier C⁵⁾ Friction 186    186    124    186    186    186    186    186 186 — modifier D⁶⁾ Friction 15   15   15   15   10   15   15   15 15 15 modifier E⁷⁾ Other additives ⁸⁾ (mass %) 17.5  17.5  17.5  17.5  17.5  17.5  17.5  17.5 17.5 17.5 Characteristics of Sample mm²/s 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.6 5.5 5.5 oils (100° C. KV) Evaluation Transmission Clutch capacity  0.112  0.115  0.116  0.114  0.112  0.110  0.108 0.114 0.120 0.121 results clutch (μs@100° C.) Lock-up Shudder 200<   200<   200<   200<   200<   200<   200<   0 0 0 clutch char- prevention acteristics lifetime (hr) ¹⁾ Base oil: a mixed base oil of 60N mineral oil and 150N mineral oil (a kinematic viscosity at 100 degrees C.: 3.0 mm²/s) ²⁾Dispersant A1: polyisobutenyl mono-succinimide (a mass average molecular weight of a polyisobutenyl group: 1300, a nitrogen amount: 1.7 mass %) ³⁾Dispersant A2: polyisobutenyl mono-succinimide (a mass average molecular weight of a polyisobutenyl group: 950, a nitrogen amount: 2.1 mass %) ⁴⁾Friction modifier B: oleylamine (a nitrogen amount: 4.7 mass %) ⁵⁾Friction modifier C: diethanol beef tallow amine (a nitrogen amount: 4 mass %) ⁶⁾Friction modifier D: isostearic acid amide (a nitrogen amount: 6.2 mass %) ⁷⁾Friction modifier E: dimethyloctadecyl amine ⁸⁾ Other additives (additive package: PMA viscosity index improver, aminic antioxidant, phenolic antioxidant, phosphorous extreme pressure agent, sulfuric extreme pressure agent, sulfuric copper deactivator, and antifoaming agent)

Evaluation Method

The sample oils were measured according to the following methods with respect to a capacity of a transmission clutch and a shudder prevention lifetime of a lock-up clutch.

Measurement results are shown in Table 1.

Capacity of Transmission Clutch

Test was conducted in accordance with M348-2002. μs (static friction coefficient) at 100 degrees C. was obtained and defined as a clutch capacity.

Shudder Prevention Lifetime of Lock-Up Clutch

Test conditions were set in accordance with JASO M349-98. A performance test was conducted during a continuous slip durability test. Specifically, a pt-V curb was obtained at 120 degrees C. and a time (hr) elapsed before dL/dV reached negative was defined as a shudder prevention lifetime.

Evaluation Results

The results in Table 1 show that the sample oils in Examples 1 to 6 containing the component (A), the component (B), the component (C), and the component (D) sufficiently exhibited both a high clutch capacity and a long shudder prevention lifetime. In contrast, the sample oils in Comparatives 1 to 4 not containing any one of the component (A), the component (B), the component (C), and the component (D) did not simultaneously exhibit a high clutch capacity and a long shudder prevention lifetime. Incidentally, Comparative 1 used the component (A2) only and Comparative 2 used the component (A1) only, in other words, Comparatives 1 and 2 do not contain the component (A). Accordingly, the sample oil of Comparative 1 exhibited a long shudder prevention lifetime but an insufficient clutch capacity. The sample oil of Comparative 2 exhibited a sufficient clutch capacity but a short shudder prevention lifetime. 

1: An automatic transmission fluid, comprising: a base oil; a component (A) comprising two or more succinimides each having an alkenyl group or an alkyl group, wherein a mass average molecular weight of the alkenyl group or the alkyl group is different in each of the succinimides; a component (B) comprising a primary amine having a carbon chain having 12 to 24 carbon atoms; a component (C) comprising an aliphatic amine alkylene oxide adduct having a carbon chain having 12 to 20 carbon atoms; and a component (D) comprising an amide compound. 2: The automatic transmission fluid according to claim 1, wherein the two or more succinimides are mono-succinimides. 3: The automatic transmission fluid according to claim 1, wherein the mass average molecular weight of the alkenyl group or the alkyl group ranges from 800 to
 1500. 4: The automatic transmission fluid according to claim 3, wherein the component (A) comprises: a mono-succinimide (A1) having an alkenyl group or an alkyl group having a mass average molecular weight in a range from 1200 to 1500; and a mono-succinimide (A2) having an alkenyl group or an alkyl group having a mass average molecular weight in a range from 800 to less than
 1200. 5: The automatic transmission fluid according to claim 4, wherein a blending ratio of the component (A1) ranges from 50 mass % to 80 mass % based on a total amount of the components (A1) and (A2). 6: The automatic transmission fluid according to claim 1, wherein a content of the component (A) range from 4.5 mass % to 6 mass % based on a total amount of the automatic transmission fluid. 7: The automatic transmission fluid according to claim 1, wherein a content of the component (B) ranges from 24 mass ppm to 235 mass ppm in terms of a nitrogen amount based on a total amount of the automatic transmission fluid. 8: The automatic transmission fluid according to claim 1, wherein a content of the component (C) ranges from 10 mass ppm to 320 mass ppm in terms of a nitrogen amount based on a total amount ofthe automatic transmission fluid. 9: The automatic transmission fluid according to claim 1, wherein a content of the component (D) ranges from 62 mass ppm to 310 mass ppm in terms of a nitrogen amount based on a total amount of the automatic transmission fluid. 